<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>求红白黑球的个数</title>
</head>

<body>
    <script type="text/javascript">
        var red, white, black;
        for (var white = 0; white <= 31; white++) {
            var red = 25 - white,
                black = 31 - white;
            if (28 == red + black) {
                alert('红球:' + red + '\n' + '白球:' + white + '\n' + '黑球:' + black);
            }
        }
    </script>
</body>

</html>